////////////////////////////////////////////////////////////////////////
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 5040
SUBJECT: GRB 060501: Swift detection of a burst
DATE: 06/05/01 08:44:00 GMT
FROM: Scott Barthelmy at NASA/GSFC
V. La Parola (INAF-IASFPA), S. D. Barthelmy (GSFC),
N. Gehrels (NASA/GSFC), V. Mangano (INAF-IASFPA),
C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL),
A. M. Parsons (GSFC), P. Romano (INAF-OAB) and E. Troja (INAF-IASFPA)
report on behalf of the Swift Team:
At 08:14:58 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 060501 (trigger=208050). Swift did not slew due to the
earth-observing constraint. The BAT on-board calculated location is
RA,Dec 328.367, +43.983 {21h 53m 28s, +43d 58' 59"} (J2000)
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows single roughly triangular
shaped peak starting at T-5 sec and ending at ~T+20 sec. The peak count rate
was ~2400 counts/sec (15-350 keV), at ~0 sec after the trigger.
Because of an Earth limb constraint, the spacecraft did not slew promptly
to the BAT position, and so there are no immediate XRT or UVOT data products
to analyze.
////////////////////////////////////////////////////////////////////////
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 5041
SUBJECT: GRB 060501: ROTSE-III Optical Limits
DATE: 06/05/01 09:19:00 GMT
FROM: Eli Rykoff at U of Michigan/ROTSE
E.S. Rykoff (U Mich), B. E. Schaefer (Louisiana State), S.A. Yost (U
Mich), R. Quimby (U Texas), report on behalf of the ROTSE collaboration:
ROTSE-IIIb, located at McDonald Observatory, Texas, responded to GRB
060501 (Swift trigger 208050, GCN 5040), producing usable images
beginning 92 s after the GCN notice time. An automated response took the
first image at 08:22:4.6 UT, 426 s after the burst, under fair
conditions with high airmass. We took 7 20-s exposures before bad
weather forced the system to close. These unfiltered images are
calibrated relative to USNO A2.0 (R).
Comparison to the DSS (second epoch) reveals no new sources within the
3-sigma error circle. Individual images have limiting magnitudes ranging
from 16.3-16.4; we set the following specific limits.
start UT end UT t_exp(s) mlim t_start-tGRB(s) Coadd?
--------------------------------------------------------------------
08:22:04.6 08:22:24.6 20 16.4 426 N
08:22:04.6 08:25:29.4 140 17.4 426 Y
////////////////////////////////////////////////////////////////////////
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 5042
SUBJECT: GRB060501: Swift XRT position
DATE: 06/05/01 15:05:02 GMT
FROM: Eleonora Troja at INAF-IASFPA
V. La Parola (INAF-IASFPa), E. Troja (INAF-IASFPa),
G. Tagliaferri (INAF-OAB), D. N. Burrows (PSU) and
J. Kennea (PSU) report on behalf of the Swift XRT Team:
The XRT attempted to centroid on GRB 060501 at 09:10:08 UT,
3309 s after the burst. However, at this late time the burst
was too faint for an on-board detection in the 2.5 s centroiding
image, and the XRT switched immediately to PC mode.
Using the first 4.5 ksec data set from the Malindi download,
we find a single weak previously uncatalogued source within the
BAT error box at:
RA: 21 53 29.9 (J2000)
Dec: +43 59 53.4 (J2000)
with 5.5 arcsec uncertainty (90% confinement).
The estimated flux is 2.6e-13 erg/sec/cm2, assuming Galactic
absorption and a power law spectrum with photon index 2.0.
This source is 58 arcsec from the BAT on-board position.
The available data do not allow us to establish if this
source is fading.
////////////////////////////////////////////////////////////////////////
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 5043
SUBJECT: GRB 060501: Refined analysis of the Swift-BAT burst
DATE: 06/05/01 15:56:31 GMT
FROM: Scott Barthelmy at NASA/GSFC
D. Palmer (LANL), L. Barbier (GSFC), S. Barthelmy (GSFC),
J. Cummings (GSFC/ORAU), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), M. Koss (UMD),
V La Parola (INAF-IASFPA), C. Markwardt (GSFC/UMD), A. Parsons (GSFC),
T. Sakamoto (GSFC/ORAU), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC)
on behalf of the Swift-BAT team:
Using the data set from T-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 060501 (trigger #208050)
(La Parola, et al., GCN 5040). The BAT ground-calculated position is
RA,Dec = 328.383,+43.993 deg {21h 53m 32.0s,+43d 59' 34.4"} (J2000)
+- 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 36%.
The mask-weighted lightcurve shows a single peak starting at T-4 sec and
ending at T+14 sec. T90 (15-350 keV) is 26 +- 2 sec (estimated error
including systematics). Because the burst location was in an Earth observing
constraint, the spacecraft then executed a slew to a preplanned target and
the new burst location went out of the BAT FOV at T+148 sec.
The time-averaged spectrum from T-1.3 to T+26.1 is best fit by
a simple power-law model. The power law index of the time-averaged
spectrum is 1.44 +- 0.15. The fluence in the 15-150 keV band is
1.2 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux measured
from T+0.36 sec in the 15-150 keV band is 1.9 +- 0.3 ph/cm2/sec.
All the quoted errors are at the 90% confidence level.
////////////////////////////////////////////////////////////////////////
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 5044
SUBJECT: GRB060501: P60 imaging and afterglow candidate
DATE: 06/05/01 16:35:26 GMT
FROM: Derek Fox at PSU
D. B. Fox (Penn State) and S. B. Cenko (Caltech) report on behalf of a
larger collaboration:
"The robotic Palomar 60-inch telescope (P60) has imaged the
localization region of GRB060501 (Swift trigger 208050; La Parola et
al., GCN 5040) in a series of exposures beginning 08:48 UT (33 minutes
after the burst). We have compared our i-band images to the
second-epoch digitized sky survey (XDSS) in a search for new sources
consistent with the XRT localization (La Parola et al., GCN 5042). We
estimate the XDSS limit in this region, by reference to USNO-B1.0
catalog photometry, as I~19.5 mag. We note that due to the location
of this field close to the Galactic plane, the background stellar
density is large and the estimated Galactic extinction (E_(B-V)~0.3
mag) is substantial. In particular, there are three star-like objects
in XDSS consistent with the XRT localization.
We find no new i-band sources within or near the XRT localization, to
a limit of I~19 mag in a coaddition of 4x60s images with mean epoch
08:58 UT (43 minutes after the burs).
A deeper coaddition of 5x150s images with mean epoch 09:47 UT (92
minutes after the burst) reveals no new source within the XRT
localization to I~21 mag. However, we do identify a single new
point-like source with I~19.3 mag, 8.1" from the center of the XRT
localization, at coordinates:
R.A. 21:53:29.52, Dec. +43:59:49.9 (J2000)
(estimated uncertainty of 0.3" in each coordinate). There is no
evidence of this source in XDSS survey images.
The source is not resolved from a neighboring star in our earlier
images, which have poorer seeing; however, these images do constrain
the object to not be significantly brighter at 43 minutes post-burst
than at our first detection, 92 minutes post-burst.
Given the absence of evidence for variability, and the distance of the
source from the XRT position, we consider the association of this
source with GRB060501 tentative at this point."
////////////////////////////////////////////////////////////////////////
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 5045
SUBJECT: GRB060501: Super-LOTIS observations
DATE: 06/05/01 20:22:13 GMT
FROM: Peter A. Milne at Super-LOTIS
P.A.Milne (Steward Obs) reports on behalf of the Super-LOTIS GRB team:
We observed the location of the BAT error circle of the GRB 060501,
as reported in GCN 5040 (Swift trigger 208050; La Parola et
al.,) using the 60cm Super-LOTIS telescope at Kitt Peak, Arizona.
Imaging began at 09:30:30 UT, 1.25 hours after the burst, and consisted
of three series of one-minute exposures in the R filter (12, 23 & 17
images per series, respectively). Seeing was typically 2.7".
A source is detected at the positionreported by Fox and Cenko (GCN 5044)
in all three summed images created from the individual exposures.
Using 8 stars from the USNO-B1 catalog, a
single image produced from the first two series led to the following
magnitudes for the suggested counterpart, R1=18.39 +/- 0.11,
R2=18.54 +/- 0.12. However, these magnitudes are very close to the
magnitude of the star 1339-0447675, which is listed at a position
consistent with the optical counterpart position listed by Fox and Cenko.
We therefore suggest that the optical counterpart candidate reported
in GCN 5044 is instead star 1339-0447675 from the USNO-B1.0 catalog.
Analysis of the last series of exposures is on-going.
////////////////////////////////////////////////////////////////////////
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 5046
SUBJECT: GRB 060501: MDM Observations
DATE: 06/05/01 22:34:01 GMT
FROM: Jules Halpern at Columbia U.
J. P. Halpern (Columbia U.) and N. Mirabal (U. Michigan) report:
"We observed the error box of Swift GRB 060501 (La Parola et al., GCN 5040)
in the R band on the MDM 1.3m telescope starting on May 01 08:28 UT,
13.4 minutes after the trigger, and continuing until 11:39 UT. Because
of poor seeing at high airmass, we were only able to detect the candidate
afterglow (Fox & Cenko, GCN 5044) near the possible X-ray afterglow
(La Parola et al., GCN 5042) beginning at 09:01 UT, or 46 minutes post-burst.
While the candidate is clearly distinguished from nearby brighter stars,
one of which was apparently measured by Milne (GCN 5045), it was not
clearly variable during the monitoring period. Although it is difficult
to measure due to contamination from nearby stars, we estimate R~20.7.
Also, because of the nearby stars, it is not possible to rule out that
it is present at this level on the POSS II, and the DSS R and I images
show a hint of it.
A finding chart for the candidate from the MDM images is available at
http://www.astro.columbia.edu/~jules/grb/060501/mdm.jpg
This message may be cited."
////////////////////////////////////////////////////////////////////////
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 5050
SUBJECT: GRB060501: Swift UVOT followup observations
DATE: 06/05/02 08:48:01 GMT
FROM: Alice Breeveld at MSSL-UCL
A. Breeveld (UCL-MSSL), V. La Parola (INAF-IASFPA), D. Vanden Berk
(PSU), F. Marshall (GSFC), on behalf of the SWIFT UVOT team:
The Swift/UVOT began taking data on the field of GRB060501 3296s after
the BAT trigger (which includes the 10s V settling exposure). Swift did
not slew immediately after the trigger because of an earth constraint
(La Parola et al., GCN 5040). At the edge of the refined XRT error
circle (La Parola et al., GCN 5042) there are two optical sources which
are already present in the USNO B1.0 catalogue, but in the summed images
there are no new sources within the error circle to the following 5
sigma upper limits:
Filter T_range(s) Exp(s) 5sig_UL(mag)
V 3296-16535 927.6 19.3
B 3626-3825 196.6 19.5
U 3422-10542 723.7 19.9
UVW1 9097-9996 885.5 20.0
UVM2 4445-4571 124.1 19.3
UVW2 4036-15788 1082.2 20.5
White (160-650nm) 3313-4030 394.6 20.0
These upper limits are uncorrected for the estimated Galactic reddening
of E(B-V) = 0.282 mags.
////////////////////////////////////////////////////////////////////////
TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 5058
SUBJECT: GRB 060501: P60 Observations and Candidate Retraction
DATE: 06/05/02 21:09:49 GMT
FROM: S. Bradley Cenko at Caltech
S. B. Cenko (Caltech) and D. B. Fox (Penn State) report on behalf of a
larger collaboration:
We have re-imaged the field of GRB 060501 (La Parola et al., GCN 5040)
with the automated Palomar 60-inch telescope. 5 x 150 s images were taken
in the i filter at a mean epoch of approximately 10:54 2 May 2006 UT (~
26.7 hours after the burst). The afterglow candidate identified by Fox
and Cenko (GCN 5044; see also Halpern and Mirabal, GCN 5046) is clearly
visible and has not faded significantly since our previous observations,
over 24 hours earlier. We therefore consider it unlikely to be the
afterglow of GRB 060501.
In addition, we find no evidence for variability in any sources in the
near vicinity of the XRT error circle (La Parola et al., GCN 5042). We
re-iterate the following limits for any afterglow emission in the XRT
error circle from our previous notice:
Limiting Magnitude Mean Time Since Burst
---------------------------------------------------------------------
I > 19.0 43 min
I > 21.0 92 min
No further observations are planned.